FIG. 1 is a schematic functional block diagram of a conventional transmitter. As shown in FIG. 1, the conventional transmitter 10 comprises a digital-to-analog converter (DAC) 12, a low pass filter (LPF) 14, a modulator 16, a programmable gain amplifier (PGA) 18 and a power amplifier 20.
The transmitter 10 is connected with an antenna (not shown) to transmit a signal to the antenna. Consequently, the antenna generates a wireless radio frequency signal to a receiver at a remote side. The programmable gain amplifier 18 and the power amplifier 20 can control the output power in order to adjust the radiation intensity of the wireless radio frequency signal.